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Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Functional Assay (Plasma/Serum)

Published: August 9, 2026Updated: August 16, 2026

This test measures how well your CFTR protein works in your blood. CFTR is important for managing salt and water balance in cells, especially in lungs, intestines, and other organs.

Quick summary

["Assesses how effectively your CFTR protein functions, which can help diagnose or monitor cystic fibrosis or related conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
43370-6
Short code
CFTRIVS8
Synonyms
CFTR IVS8 PolyT Bld/T Ql
Category
chemistry
Sample
whole-blood
Container
EDTA (purple-top) whole blood tube for peripheral blood samples; sterile container for tissue specimens; ACD (yellow-top) tube is also acceptable
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
molgen
CPT
81220
SNOMED
444875009
Specimen volume
3-5 mL whole blood; minimum 1 mL for pediatric samples; fresh or frozen tissue as appropriate
Stability
Whole blood stable at room temperature (18-25°C) for 24-48 hours; refrigerated (2-8°C) for up to 7 days; frozen (-20°C or lower) for long-term storage. DNA extracted from blood is stable for years when stored at -20°C or -80°C. Tissue specimens should be frozen at -80°C or processed promptly.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
72–336 hours
Order
routine

Why This Test Matters

Cystic fibrosis (CF) is a genetic disorder that affects how your body moves salt and water. The CFTR protein helps regulate these processes. If this protein doesn’t work properly, it can lead to thick mucus buildup in organs like the lungs and pancreas, causing health problems. This test helps doctors understand if your CFTR protein is functioning as it should, which can guide treatment decisions.

What to Expect Before the Test

No special preparation is usually needed for this test. You may have a blood sample drawn from a vein in your arm, similar to other blood tests. If you’re being tested for CFTR function in a different body fluid (like sweat or saliva), your doctor will provide specific instructions.

What the Results Mean

Results from this test help determine if your CFTR protein is working normally. Low or abnormal function may indicate CF or other conditions affecting salt/water transport. Your doctor will interpret the results in the context of your symptoms and medical history.

Common Reasons for This Test

Doctors may order this test if you have symptoms of CF (like chronic lung infections, poor weight gain, or digestive issues), if you have a family history of CF, or if you’re being evaluated for CFTR-related disorders.

Reference range

Poly-T tract genotypes reported as 5T/5T, 5T/7T, 5T/9T, 7T/7T, 7T/9T, or 9T/9T. The 7T and 9T alleles are considered normal/non-pathogenic. The 5T allele in homozygous or compound heterozygous state (in trans with a CFTR mutation) is associated with reduced CFTR mRNA splicing efficiency and may contribute to CFTR-related disorders including congenital bilateral absence of the vas deferens (CBAVD), mild cystic fibrosis, or atypical CF presentations.N/A

Specimen: whole-blood

No special patient preparation required. Patients should provide informed consent for genetic testing and genetic counseling is recommended. A detailed family history of cystic fibrosis or CFTR-related disorders should be documented.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CFTR Function Test

Frequently asked questions

What causes abnormal CFTR function?
Abnormal CFTR function can be caused by genetic mutations that disrupt the protein’s ability to regulate salt and water movement. These mutations are often inherited and linked to cystic fibrosis or other ion transport disorders.
How does this test differ from a sweat test?
While both tests assess CFTR function, the sweat test measures chloride levels in sweat, whereas this test evaluates CFTR’s functional activity in blood. The blood test can also help monitor treatment effects over time.
Can this test be done at home?
No, this test requires a medical professional to collect a blood or other body fluid sample in a clinical setting. Some specialized CF centers may offer at-home sweat tests, but the plasma/serum CFTR function test is typically performed in a lab.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy